1. Field of the Invention
The present invention relates to a method and apparatus for the non-invasive detection and monitoring of a physiological state or medical condition by monitoring peripheral arterial tone ("PAT"). More specifically, the present invention relates to monitoring changes in the peripheral arterial vasoconstriction in reaction to such state or condition, particularly those related to cardiopulmonary distress and blood pressure in order to detect or monitor the physiological state or medical condition of the patient.
2. Description of Related Art
As noted above, the present invention relates to detection and monitoring of various physiological states and medical conditions by detecting hemodynamic events in body extremity of the patient. However, while the present invention relates to detecting and monitoring numerous physiological states and medical conditions, four particular examples generally related to cardiopulmonary distress and blood pressure are provided herein; namely, myocardial ischemia, sleep staging, sleep apnea syndrome, and continuous blood pressure monitoring. Therefore, the following discussion includes description of art related to these four examples.
In addition, it appears that the present invention may be useful in detecting coronary artery disease ("CAD") and endothelial dysfunction ("ED"). A prior art technique for detecting ED is described briefly at the end of this section.
Further, the present invention is also useful in connection with mental stress tests for detecting coronary artery disease. A brief description of conventional mental stress testing is provided at the end of this section.